Ritz vector approach for evaluating incabinet response spectra Original Research Article

A new method is proposed for evaluating accurate incabinet response spectra for seismic qualification of electrical instruments. Finite element analysis of several typical cabinets shows that only few (often one) modes contribute significantly to the spectral accelerations at critical instrument locations inside the cabinet. In most cases the significant mode is a local mode of the cabinet component like door or back wall on which the instrument is mounted. In some cases it can also be a global cabinet mode or a superposition of the global cabinet and local component modes. Dynamic properties of the significant modes can be calculated using Rayleigh–Ritz method. The engineering effort and computational time taken by the new method is a minute fraction of that by the finite element method.